Practice Questions

mRNA must exit the nucleus to be translated into protein. Blocking export stalls translation in the cytoplasm.

Cyclin-dependent kinases phosphorylate nuclear lamins, causing the intermediate filaments to depolymerize and dismantle the nuclear structural border.

Nucleolar Organizer Regions (NORs) contain the repeating loops of DNA encoding rRNA genes around which the nucleolus forms.

Proteins destined for the nucleus possess a Nuclear Localization Signal (NLS) that is recognized by importin proteins for active transport through the pore.

Karyolymph or nucleoplasm fluid forms the soluble matrix inside the nucleus, supporting chemical activities.

Heterochromatin is tightly packed, dark-staining, and transcriptionally silent, whereas euchromatin is loosely packed and active.

High protein synthesis demands rapid ribosome production, which directly causes the hypertrophy of the nucleolus to produce rRNA.

The nuclear lamina is an intermediate filament meshwork lining the inner nuclear membrane, providing structural support and anchoring chromatin.

Nuclear pores span the double membrane of the nucleus, serving as controlled gates for macromolecular transit. Plasmodesmata are plant cell junctions.

Chromatin is the relaxed, operational thread-like network of DNA complexed with histone proteins visible during interphase. Chromatids and chromosomes represent highly condensed stages.